LEL Sensor Precautions
For safety reasons, EXO must be operated and serviced by qualified personnel only. Read and understand the information below before operating or servicing.
Off-scale (overlimit) readings may indicate an explosive concentration.
Calibrations must only be performed in areas free of flammable gases.
Blackline’s LEL sensors can be calibrated with the following settings:
| Gas | Calibration concentration (%vol) | Calibration concentration (%LEL) | Balance |
|---|---|---|---|
| Methane (CH4) | 2.5% | 50% ±2% | Standard quad-gas mixture |
No known gases desensitize or contaminate Blackline’s LEL-MPS and LEL-IR sensors. These two sensors do not cause any electromagnetic interference (EMI), and are not negatively affected by EMI, such as radio transmissions, of up to 8W.
Some compounds will decompose on the catalyst of the LEL-P and form a solid barrier over the catalyst surface. This action is cumulative, and prolonged exposure will result in an irreversible decrease in sensitivity. The most common of these substances are compounds containing lead or sulphur, silicones, and phosphates.
Some other compounds, especially hydrogen sulphide and halogenated hydrocarbons, are absorbed or form compounds that are absorbed by the catalyst of the LEL-P. The resulting loss of sensitivity is temporary. In most cases a sensor will recover after a period of operation in clean air.
Like any gas sensor, be sure to understand potential explosive hazards and choose the appropriate sensor technology based on these hazards.
Blackline Safety supports three different LEL sensor technologies:
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Molecular Property Spectrometer (LEL-MPS)
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Non-Dispersive Infra-Red (LEL-IR)
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Pellistor (catalytic bead) (LEL-P) (EU/UK only)
LEL sensors cannot be disabled in Blackline Live.
Molecular Property Spectrometer (LEL-MPS)
This sensor is not intended for inert environments. Environments with oxygen (O2) levels below 18% will negatively impact this sensor's accuracy and Blackline does not recommend using it when oxygen levels are below 10%.
LEL-MPS sensors must be started in clean air and zeroed upon start-up to function properly. EXO devices equipped with LEL-MPS sensors cannot perform an automatic zeroing of the LEL-MPS sensor without manual confirmation.
| LEL-MPS sensors must be started in clean air and zeroed upon start-up to function properly. EXO devices equipped with LEL-MPS sensors cannot perform an automatic zeroing of the LEL-MPS sensor without manual confirmation. | |
| When powering on an EXO with an LEL-MPS sensor, the device will prompt you to acknowledge and approve that the device has been powered on in a clean air environment and a zero adjustment can take place. Should you fail to acknowledge the zero prompt within 15 seconds, your device will enter a latched alarm state and require that you power cycle the device and approve the zero prompt. |
The clean air confirmation prompt is configurable in Blackline Live. If the clean air confirmation prompt is disabled, the device will prompt you to perform a manual zero adjustment.
When bump testing or calibrating this sensor, apply a gas mixture containing at least 18% oxygen (O2). Less oxygen than this may negatively impact the sensor's readings. If a gas mixture with less than 18% oxygen is applied during a bump test or calibration, restart EXO to auto zero the sensor.
This sensor can be calibrated two ways: default calibration and full calibration.
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The default calibration procedure will validate and ensure accuracy without adjusting the LEL-MPS sensor's readings. Unlike traditional sensors, this sensor is factory-calibrated for optimal accuracy. We recommend using the factory calibration for the lifetime of the sensor.
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Advanced users can perform a full calibration with a span adjustment. A full calibration may negatively impact the accuracy of other gases. EXO can be configured to run a full calibration on this sensor in Blackline Live.
Non-Dispersive Infra-Red (LEL-IR)
This sensor can function in inert environments without oxygen. This sensor does not detect Hydrogen (H) or Acetylene (C2H2).
Pellistor (catalytic-bead) (LEL-P)
Any rapid up-scale reading followed by declining or erratic reading may indicate a gas concentration beyond upper scale limit, which may be hazardous.
